The present invention relates to a method and a device for determining a quantity describing the height of the center of gravity of a vehicle.
Various versions of methods and devices for determining a quantity describing the height of the center of gravity of a vehicle are described in the related art.
German Patent No. 32 22 149 C2 describes a device for preventing a vehicle from tilting sideways. This device contains, among other things, a means for calculating the height of the overall center of gravity of the vehicle. This vehicle is a straddle loader for shipping large-volume containers. In calculating the height of the overall center of gravity of the vehicle, it is assumed that both the weight of the straddle loader and the height of the center of gravity of the straddle loader are known. The height and weight of the container are each determined by a measuring device. The height of the center of gravity of the vehicle is determined from the weight of the straddle loader, the height of the center of gravity of the straddle loader, the weight of the container and the height of the center of gravity of the container.
German Patent No. 44 16 991 A1 describes a method and device for warning a truck driver of rollover danger in turning a corner. To do so, the type of vehicle and status information, such as the vehicle weight and speed relevant to the risk of tilting when turning, are determined before the vehicle enters the curve. The risk of tilting when turning at the detected driving speed is determined as a function of the center of gravity of the vehicle mass and the radius of the curve. At least a signal indicating excessive driving speed is triggered if it is found that there is a danger of tilting or if the vehicle is below a predetermined safety margin for the risk of tilting.
The total weight of the vehicle is determined as follows: wheel load sensors are provided in a line across the direction of travel in the straightest possible stretch of roadway before a curve. The total weight is determined by taking the sum of the wheel loads detected by the individual wheel load sensors. Furthermore, a sensor is provided before the curve for detecting the height and height contour of the respective vehicle. Thus, the weight-dependent height of the center of gravity of the vehicle can be estimated as a function of the total weight of the vehicle, its height and height contour as well as selected information about the type of vehicle specified.
An object of the present invention is to improve existing methods and devices for determining a quantity describing the height of the center of gravity of a vehicle.
With the method according to the present invention for determining at least one quantity describing the height of the center of gravity of the vehicle, a quantity describing the wheel rpm is determined for at least one wheel. For this at least one wheel, a quantity describing the wheel performance is determined at least as a function of the wheel rpm of the corresponding wheel. A quantity describing the height of the center of gravity of the vehicle is determined at least as a function of the quantity determined for the minimum of one wheel, which describes the wheel performance of this wheel.
The method according to the present invention for determining at least one quantity describing the height of the center of gravity of the vehicle is advantageously used within the context of a method of stabilizing the vehicle. In particular, the method according to the present invention is used within the context of a method of preventing vehicle rollover. It is especially advantageous if a velocity parameter is determined at least as a function of at least one quantity describing the height of the center of gravity of the vehicle, and if a determination is made at least as a function of this velocity parameter as to whether there is a tendency for the vehicle to tilt about a vehicle axis oriented in the longitudinal direction of the vehicle. If the vehicle does have a tendency to tilt, at least one braking measure is advantageously performed on at least one wheel, and/or engine measures and/or chassis actuators are initiated in order to stabilize the vehicle, in particular to prevent the vehicle from turning over.
The phrase xe2x80x9ca vehicle axis oriented in the longitudinal direction of the vehiclexe2x80x9d is understood as follows: first, the vehicle axis about which the vehicle has a tendency to tilt may be the actual longitudinal axis of the vehicle. Second, it may be a vehicle axis which is twisted about a certain angle with respect to the actual longitudinal axis of the vehicle. It does not matter whether the twisted vehicle axis passes through the center of gravity of the vehicle. The case of the twisted vehicle axis should also permit an orientation of the vehicle axis such that the vehicle axis corresponds either to a diagonal axis of the vehicle or an axis parallel to that.
It is advantageous to determine the quantity describing the height of the center of gravity as a function of the drive slip and/or wheel slip prevailing on at least one wheel as compared with a corresponding threshold value. On the basis of this comparison, different determinations of the at least one quantity describing the height of the center of gravity of the vehicle can be performed. Thus, if the value of the drive slip and/or wheel slip prevailing on at least one wheel is smaller than the corresponding threshold value, the corresponding quantity describing the height of the center of gravity of the vehicle is determined at least as a function of the quantity describing the wheel performance which was determined for the minimum of one wheel in the present time increment. However, if the value of the drive slip and/or wheel slip determined for the minimum of one wheel is greater than the corresponding threshold value, the corresponding quantity describing the height of the center of gravity of the vehicle is determined at least as a function of the quantity describing the wheel performance which was determined for the minimum of one wheel in a preceding time increment.
A quantity depending on the wheel load acting on the respective wheel is determined advantageously as the quantity describing the wheel performance of the respective wheel. For example, quantities describing the diameter or radius of the respective wheel are especially advantageous because a curve-induced displacement of the center of gravity of the vehicle has an especially strong effect on the diameter of the vehicle wheels. Therefore, a displacement of the center of gravity of a vehicle and a consequent tendency of the vehicle to tilt can be detected directly on the basis of vehicle wheel diameter.
The quantity describing wheel performance of the respective wheel is advantageously determined at least as a function of the quantity describing the wheel rpm of the respective wheel, a quantity describing the vehicle speed, a quantity representing the transverse dynamics of the vehicle and a quantity describing the geometry of the vehicle. The quantity describing vehicle speed is determined at least as a function of the quantities describing the wheel rpm determined for the wheels. The quantity representing the transverse dynamics of the vehicle may advantageously be a quantity describing the yaw and/or transverse acceleration of the vehicle.
The corresponding quantity describing the height of the center of gravity of the vehicle is advantageously determined at least as a function of a quantity describing the performance of a wheel axle, corresponding in particular to a quantity describing the angle of inclination of the wheel axle to the road surface. The quantity describing the performance of the wheel axle is determined at least as a function of the quantities determined for the wheels on one axle, describing the wheel performance, and taking into account a quantity representing the vehicle geometry.
In determining the corresponding quantity describing the height of the center of gravity of the vehicle, not only is the quantity describing the performance of the wheel axle taken into account, but a quantity describing the transverse dynamics of the vehicle, a quantity describing the load acting on the wheel axle, a quantity describing the vehicle geometry and a quantity representing rigidity, in particular the resulting vertical rigidity of the wheels on the respective wheel axle, are also taken into account.